Fresh evidence of the dramatic impact of the Greek debt crisis on the health of the country’s finances has emerged, with official figures showing tax revenues collapsing.

As talks continued over a proposed €86bn third bailout of the stricken state, the Greek treasury said tax revenues were 8.5% lower in the first six months of 2015 than the same period a year earlier. The bank shutdown that brought much economic activity to a halt began on 28 June.

Public spending fell even more dramatically, by 12.3%, even before the new austerity measures the prime minister Alexis Tsipras has been forced to pass to win the support of his creditors for talks on a new bailout.

Greece is due to make a €3.2bn repayment to the European Central Bank on 20 August.

Talks with the quartet of creditors, which includes the ECB, the International Monetary Fund, the European commission and Europe’s bailout fund, the European stability mechanism, are continuing, and Tsipras has suggested they are “in the final stretch”.

However, it remains unclear whether the prime minister, who was only able to pass the latest package of austerity measures with the help of opposition MPs, will be able to win the backing of his radical Syriza party for new reforms, at a special conference due to be held next month.

The IMF has made clear that it will refuse to commit any new funds until Greecehas signed up to a new economic reform programme, and eurozone countries have made a concrete offer to write off part of the country’s debt burden.

Sweden’s representative on the 24-member IMF board, Thomas Östros, said there was strong support for a new Greek rescue, “but it will take time”.

He also noted that Greece must adopt wide-ranging reforms first. “They have an inefficient public sector, corruption is a relatively big problem and the pension system is more expensive than other countries.”

Despite the grim news on the public finances, Greek stock markets bounced back yesterday, after three straight days of decline, with the main Athens index closing up 3.65%.

In a separate piece of more optimistic news, official figures showed that the unemployment rate has fallen to its lowest level in three years – though it remains at a historic high of 25%.